Subject: Re: [Fot] Intake / Exhaust manifold mating surfaces to head

From: Tony Drews <[email-masked]>
Date: Tue, 07 Oct 2014 21:49:06 -0500

You're very liable to make things worse by opening up the 
manifold.  Having the manifold port somewhat smaller than the head 
port isn't a big problem.

Tony Drews

At 02:46 PM 10/7/2014, Dan wrote:
>I am preparing my TR4a head to accept the intake and exhaust manifolds and
>there seems to be a rather significant difference in the diameters between the
>intake ports of the head (1-1/2" dia.) and the intake manifold (1-3/8 to
>1-7/16" dia.). In addition, the two mating gaskets I measured come in with a
>dia. of 1-23/32nd, just under 1-3/4".  The literature I have consulted
>recommends that the intake ports of the head and the manifold match up
>perfectly including the dia. of the mating gaskets.  Not so critical on the
>exhaust  as a "notch" to the upside on the exhaust port apparently aids in
>extracting gases.  What have you all found in your engine building
>experiences?  I could carefully enlarge the intake ports to match the head,
>but the remaining intake  (TR4a long runner) shell would need to be a opened
>up around 7/32nds thereby perhaps weakening the runners?  Thoughts?
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From: Duncan Charlton <[email-masked]>
Date: Wed, 08 Oct 2014 08:10:23 -0500

My book sources indicate that it's fine for the intake manifold runner 
to be slightly smaller than the port entrance on the head, and the 
opposite goes for the exhaust port/manifold junction. Pulsing pressure 
waves revert upstream due to valve closure and leaving a lip at the 
outer edge theoretically blocks the reversion wave to some extent.  It's 
OK to have a "downward" step for the gases to fall over but you don't 
want an "upward" step for the gases to have to pass over.

Duncan
(Texas)

On 10/7/14, 9:49 PM, Tony Drews wrote:
> You're very liable to make things worse by opening up the manifold.  
> Having the manifold port somewhat smaller than the head port isn't a 
> big problem.
>
> Tony Drews
>
> http://autox.team.net/mailman/options/fot/[email-masked]

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From: Dan Cronin <[email-masked]>
Date: Wed, 8 Oct 2014 15:57:31 -0400

10/8
Thanks to all who took the time to read my query and respond.  Very
interesting variety of thought on wether or not matching the ports is a big
deal --- or not (as long as the gas / exhaust flows from smaller to larger
bores).
Dan

On Oct 7, 2014, at 3:46 PM, Dan <[email-masked]> wrote:

there seems to be a rather significant difference in the diameters between
the

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From: John Styduhar <[email-masked]>
Date: Wed, 8 Oct 2014 17:06:05 -0400

You should read what Kas has to say in his prep manual..  He recommends
port matching.

On Wed, Oct 8, 2014 at 3:57 PM, Dan Cronin <[email-masked]> wrote:

> http://autox.team.net/mailman/options/fot/[email-masked]

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From: Tony Drews <[email-masked]> mail.com>
Date: Thu, 09 Oct 2014 14:57:40 -0500

A little more on port matching - what Jack found working on the flow 
bench is that if you open up the intake runner ID too quickly you 
kill the flow through the manifold.  The air delaminates from the 
surface and becomes turbulent.  You need to keep the change in ID to 
under 7 degrees of taper.  Also, look at the port in the head - some 
of them had a ball mill shoved in for a short distance and the inner 
port diameter is much smaller.  In that case you may be better off 
adding epoxy to the port in the head to make it more of a straight shot.

He also found that a step from smaller diameter to larger diameter in 
the direction of flow wasn't very harmful to overall flow.
http://www.tonydrews.com/uncle_jacks_engine_building_tips.htm#Head

Tony Drews

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From: John Styduhar <[email-masked]>
Date: Tue, 14 Oct 2014 10:12:49 -0400

The latest model of  bare TR2-4 cylinder heads with casting 11695 and 1 1/2
intake ports at the face (cleaned and manafluxed) are available from Team
Triumph in Warren, OH.  Give Scott Harper a call at 303-392-7176.

On Thu, Oct 9, 2014 at 3:57 PM, Tony Drews <[email-masked]> wrote:

> A little more on port matching - what Jack found working on the flow bench
> is that if you open up the intake runner ID too quickly you kill the flow
> through the manifold.  The air delaminates from the surface and becomes
> turbulent.  You need to keep the change in ID to under 7 degrees of taper.
> Also, look at the port in the head - some of them had a ball mill shoved in
> for a short distance and the inner port diameter is much smaller.  In that
> case you may be better off adding epoxy to the port in the head to make it
> more of a straight shot.
>
> He also found that a step from smaller diameter to larger diameter in the
> direction of flow wasn't very harmful to overall flow.
>> > 1-7/16" dia.). In addition, the two mating gaskets I measured come in
>> with
>> > a